Done this for years. I don't call it "parasite" since you are giving them the service of providing content.

But I've learned to have the main, long post on your own site and post-point from these others to your site-blog-content.

What is needed is to check Alexa for each of these to see what they actually get as traffic - and what they can send to you. My Blogger posts show up on Google pretty fast; I don't know about these others. Time to brush off my old Geocities sites and see if they are still there...